[Info-vax] HP wins Oracle Itanium case

[David Froble]

Paul Sture wrote:
> On Tue, 28 Aug 2012 14:39:09 -0400, Stephen Hoffman wrote:
> 
>> On 2012-08-28 16:58:35 +0000, Bob Koehler said:
>>
>>>    Blows away folks when I access a keyed-indexed file "sequentially".
>> You're either being humored with that "blown away", or you're discussing
>> this with folks that are ignorant of how databases work. What you're
>> discussing goes back to the S in the IBM Indexed Sequential Access
>> Method ISAM scheme, and which well predates RMS.
>> If not earlier.
>> Microsoft Access offers ISAM access, as does MySQL, BerkelyDB, dBase and
>> a whole pile of other packages.
> 
> One key difference (pun unintended) with RMS ISAM files from the ones I 
> had worked with previously was that after the initial file load RMS will 
> add new records so that key and record data are interspersed physically 
> within the file.  IIRC this was the result of a design goal to provide 
> fast sequential read access.
> 
> This was detailed in the RMS-11 User Guide; unfortunately (IMHO at the 
> time) this level of detail didn't reach the VMS 4.0 or later 
> documentation.
> 
> With modern storage arrays which simply present a bunch of blocks, decent 
> buffer and cache sizes probably make more difference today.
> 

When RMS needs additional storage, it extends the file.  Clusters 
(buckets), key or data, are added as needed.  As far as I know it's 
nothing more than that.

Key clusters have pointers to the next cluster to allow sequential 
reading of the data by the selected key.

Data records and the bottom level primary key are one and the same.

It's been a while, and I don't remember if the key clusters have back 
pointers, allowing a descending sequential access.  It is something i 
designed for my database, but never got around to implementing.